Discrete GPU Performance (Underclocked CPU)

**Please note that for the R7 260X, we raised the CPU clock speed slightly from 2.8GHz to 3GHz (still a significant underclock) as the lower speed was causing instability and crashes.**



These tests are designed to simulate a more CPU-limited scenario than our usual test rig. However, at 2,560 x 1,440 using ultra settings, the R9 290X results are essentially unaffected, with Mantle still providing a 6 percent performance gain. Dropping to medium does lower the framerates for both APIs, but the Mantle advantage is no greater than before at 7 percent.



At 1080p, the ultra preset still appears to be mostly GPU-limited, no doubt thanks to the taxing 4x MSAA setting that comes with it. It's only the R9 290X which sees a benefit here, again of about 6 percent, while Mantle brings no advantage to either the R9 280X or R7 260X. Finally, with a throttle CPU and the medium detail setting, the GPU limit appears to lift somewhat, as all three cards see their biggest gains in this test. The R9 290X rockets up by 37 percent – an impressive feat but equally not one that the human eye is likely to see given that it goes from 126fps to 173fps. Likewise, the gains on the lower cards do not matter too much, as the framerate is already well above 60fps in each case.